Prothena Corp
PRTA
185 hedge funds and large institutions have $457M invested in Prothena Corp in 2026 Q1 according to their latest regulatory filings, with 29 funds opening new positions, 68 increasing their positions, 50 reducing their positions, and 22 closing their positions.
100% more funds holding in top 10
Funds holding in top 10: 1 → 2 (+1)
45% more call options, than puts
Call options by funds: $3.61M | Put options by funds: $2.48M
36% more repeat investments, than reductions
Existing positions increased: 68 | Existing positions reduced: 50
32% more first-time investments, than exits
New positions opened: 29 | Existing positions closed: 22
2% more funds holding
Funds holding: 181 → 185 (+4)
1% more capital invested
Capital invested by funds: $452M → $457M (+$5.06M)
0.51% less ownership
Funds ownership: 87.78% → 87.27% (-0.51%)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
RCMNY
Rubric Capital Management (New York)
New York
|
+$12.1M |
| 2 |
BlackRock
New York
|
+$4.92M |
| 3 |
Two Sigma Investments
New York
|
+$4.91M |
| 4 |
PM
Penbrook Management
New York
|
+$2.49M |
| 5 |
MCM
Monimus Capital Management
Woodbridge,
New Jersey
|
+$2.12M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
AC
Armistice Capital
New York
|
-$9.72M |
| 2 |
Citadel Advisors
Miami,
Florida
|
-$4.37M |
| 3 |
Point72 Asset Management
Stamford,
Connecticut
|
-$4.22M |
| 4 |
State Street
Boston,
Massachusetts
|
-$3.02M |
| 5 |
Jane Street
New York
|
-$2.94M |
PRTA Hedge Fund Activity: Q1 2026 in Review
185 institutional investors reported a position in Prothena Corp (PRTA) for Q1 2026, worth a combined $457M — up 1.1% from $452M a quarter earlier.
Buyers outnumbered sellers: 29 funds opened new PRTA positions and 22 closed out — a net gain of 7 holders — while 68 added to existing stakes and 50 trimmed.
The largest buyer was Rubric Capital Management (New York), adding an estimated $12.1M. The largest seller was Armistice Capital, cutting an estimated $9.72M.
- 185 institutional investors held Prothena Corp (PRTA) as of Q1 2026, up from 181 in Q4 2025.
- Funds reported $457M of Prothena Corp stock for Q1 2026, up 1.1% quarter-over-quarter.
- 29 funds opened new Prothena Corp positions in Q1 2026 and 22 closed out, a net change of +7 holders.
- The largest Prothena Corp buyer in Q1 2026 was Rubric Capital Management (New York), an estimated $12.1M added.
- The largest Prothena Corp seller in Q1 2026 was Armistice Capital, an estimated $9.72M sold.
Based on aggregated 13F filings for Q1 2026.